Seal bearing and image forming apparatus

Abstract

A seal bearing includes: a bearing part configured to bear and hold a shaft such that the shaft is rotatable; and a seal part made of elastomer and combined with the bearing part. The seal part is joined to an end surface among two end surfaces of the bearing part. The two end surfaces are adjacent to a bearing surface of the bearing part in an axial direction.

What is claimed is: 
     
       1. A seal bearing comprising:
 a bearing part configured to bear and hold a shaft such that the shaft is rotatable; and 
 a seal part made of elastomer and combined with the bearing part, wherein 
 the seal part is joined to an end surface among two end surfaces of the bearing part, the two end surfaces being adjacent to a bearing surface of the bearing part in an axial direction; 
 wherein
 the bearing part is made of resin, 
 
 a difference between a solubility parameter of the bearing part and a solubility parameter of the seal part is equal to or less than 1 cal/ml, and 
 the seal part is welded to the end surface. 
 
     
     
       2. The seal bearing according to  claim 1 , wherein the seal part is also joined to a surface of the bearing part that is adjacent to the end surface and that faces in a different direction from the end surface. 
     
     
       3. The seal bearing according to  claim 1 , wherein a solubility parameter of the seal part is equal to or less than 9 cal/ml. 
     
     
       4. The seal bearing according to  claim 1 , wherein
 the bearing part is made of polypropylene, and 
 the seal part is made of elastomer that contains polypropylene as matrix resin. 
 
     
     
       5. The seal bearing according to  claim 4 , wherein the seal part is made of polystyrene thermoplastic elastomer or olefin thermoplastic elastomer. 
     
     
       6. The seal bearing according to  claim 1 , wherein the seal part has a level of hardness equal to or less than A70. 
     
     
       7. The seal bearing according to  claim 1 , wherein
 the seal part includes an end portion that is opposite a joint end surface of the seal part joined to the bearing part and that is in contact with the shaft borne and held by the bearing part, and 
 the end portion of the seal part is equal to or less than  2  millimeters in thickness. 
 
     
     
       8. The seal bearing according to  claim 1 , wherein
 the seal part includes an end portion that is opposite a joint end surface of the seal part joined to the bearing part and that is in contact with the shaft borne and held by the bearing part, and 
 the seal part is thinner at the end portion than at the joint end surface. 
 
     
     
       9. The seal bearing according to  claim 1 , wherein
 the seal part includes an end portion that is opposite a joint end surface of the seal part joined to the bearing part and that is in contact with the shaft borne and held by the bearing part, and 
 when the bearing part does not bear the shaft and the seal part receives no load, the end portion of the sealing part enters inside a position of an inner diameter of the bearing surface such that a ratio of a length of the end portion entering inside the position of the inner diameter in a radial direction to the inner diameter is equal to or less than 10%. 
 
     
     
       10. The seal bearing according to  claim 1 , wherein
 the seal part includes an end portion that is opposite a joint end surface of the seal part joined to the bearing part and that is in contact with the shaft borne by the bearing part, and 
 the seal part is shaped such that an inner diameter of the seal part changes along an axial direction so as to gradually decrease from the joint end surface toward the end portion. 
 
     
     
       11. The seal bearing according to  claim 10 , wherein
 when the end portion of the seal part is assumed to be a top and the joint end surface of the seal part is assumed to be a bottom, an external shape of the seal part is asymmetrical in a top-bottom direction. 
 
     
     
       12. The seal bearing according to  claim 1 , wherein the bearing part is a sliding bearing that bears the shaft on an internal circumferential surface as the bearing surface. 
     
     
       13. The seal bearing according to  claim 12 , wherein
 the bearing part includes a hollow that communicates with the bearing surface through to a surface different from the bearing surface. 
 
     
     
       14. An image forming apparatus comprising:
 an electrophotographic image former that develops an electrostatic latent image with toner; and 
 the seal bearing according to  claim 1 , wherein 
 the seal bearing is positioned at boundaries of a toner space where toner is placed and an external space so as to hold the shaft that passes through the toner space and the external space, 
 the seal part is positioned at the toner space side, and 
 an outer diameter of the shaft (pa, an inner diameter of the bearing surface φb, and an inner diameter of the seal part (φc satisfy φc<φa<φb.